//==========================================================================
// Copyright (c) 2000-2008,  Elastos, Inc.  All Rights Reserved.
//==========================================================================
/*** WARNING - THIS HAS NEVER BEEN FINISHED ***/
/*****************************************************************************
* chap.c - Network Challenge Handshake Authentication Protocol program file.
*
* Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
* portions Copyright (c) 1997 by Global Election Systems Inc.
*
* The authors hereby grant permission to use, copy, modify, distribute,
* and license this software and its documentation for any purpose, provided
* that existing copyright notices are retained in all copies and that this
* notice and the following disclaimer are included verbatim in any 
* distributions. No written agreement, license, or royalty fee is required
* for any of the authorized uses.
*
* THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS *AS IS* AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
* IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
******************************************************************************
* REVISION HISTORY
*
* 03-01-01 Marc Boucher <marc@mbsi.ca>
*   Ported to lwIP.
* 97-12-04 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
*	Original based on BSD chap.c.
*****************************************************************************/
/*
 * chap.c - Challenge Handshake Authentication Protocol.
 *
 * Copyright (c) 1993 The Australian National University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the Australian National University.  The name of the University
 * may not be used to endorse or promote products derived from this
 * software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Copyright (c) 1991 Gregory M. Christy.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by Gregory M. Christy.  The name of the author may not be used to
 * endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#include "ppp.h"
#if PPP_SUPPORT > 0
#include "magic.h"

#if CHAP_SUPPORT > 0

#include "randm.h"
#include "auth.h"
#include "md5.h"
#include "chap.h"
#include "chpms.h"
#include "pppdebug.h"

/*************************/
/*** LOCAL DEFINITIONS ***/
/*************************/

/************************/
/*** LOCAL DATA TYPES ***/
/************************/

/***********************************/
/*** LOCAL FUNCTION DECLARATIONS ***/
/***********************************/
/*
 * Protocol entry points.
 */
static void ChapInit (int);
static void ChapLowerUp (int);
static void ChapLowerDown (int);
static void ChapInput (int, u_char *, int);
static void ChapProtocolReject (int);
static int  ChapPrintPkt (u_char *, int,
                  void (*) (void *, char *, ...), void *);

static void ChapChallengeTimeout (void *);
static void ChapResponseTimeout (void *);
static void ChapReceiveChallenge (chap_state *, u_char *, int, int);
static void ChapRechallenge (void *);
static void ChapReceiveResponse (chap_state *, u_char *, int, int);
static void ChapReceiveSuccess(chap_state *cstate, u_char *inp, u_char id, int len);
static void ChapReceiveFailure(chap_state *cstate, u_char *inp, u_char id, int len);
static void ChapSendStatus (chap_state *, int);
static void ChapSendChallenge (chap_state *);
static void ChapSendResponse (chap_state *);
static void ChapGenChallenge (chap_state *);

/******************************/
/*** PUBLIC DATA STRUCTURES ***/
/******************************/
chap_state chap[NUM_PPP];  /* CHAP state; one for each unit */

struct protent chap_protent = {
    PPP_CHAP,
    ChapInit,
    ChapInput,
    ChapProtocolReject,
    ChapLowerUp,
    ChapLowerDown,
    NULL,
    NULL,
#if 0
    ChapPrintPkt,
    NULL,
#endif
    1,
    "CHAP",
#if 0
    NULL,
    NULL,
    NULL
#endif
};

/*****************************/
/*** LOCAL DATA STRUCTURES ***/
/*****************************/
static char *ChapCodenames[] = {
    "Challenge", "Response", "Success", "Failure"
};

/***********************************/
/*** PUBLIC FUNCTION DEFINITIONS ***/
/***********************************/
/*
 * ChapAuthWithPeer - Authenticate us with our peer (start client).
 *
 */
void ChapAuthWithPeer(int unit, char *our_name, int digest)
{
    chap_state *cstate = &chap[unit];

    cstate->resp_name = our_name;
    cstate->resp_type = digest;

    if (cstate->clientstate == CHAPCS_INITIAL ||
        cstate->clientstate == CHAPCS_PENDING) {
        /* lower layer isn't up - wait until later */
        cstate->clientstate = CHAPCS_PENDING;
        return;
    }

    /*
     * We get here as a result of LCP coming up.
     * So even if CHAP was open before, we will 
     * have to re-authenticate ourselves.
     */
    cstate->clientstate = CHAPCS_LISTEN;
}

/*
 * ChapAuthPeer - Authenticate our peer (start server).
 */
void ChapAuthPeer(int unit, char *our_name, int digest)
{
    chap_state *cstate = &chap[unit];

    cstate->chal_name = our_name;
    cstate->chal_type = digest;

    if (cstate->serverstate == CHAPSS_INITIAL ||
        cstate->serverstate == CHAPSS_PENDING) {
        /* lower layer isn't up - wait until later */
        cstate->serverstate = CHAPSS_PENDING;
        return;
    }

    ChapGenChallenge(cstate);
    ChapSendChallenge(cstate);  /* crank it up dude! */
    cstate->serverstate = CHAPSS_INITIAL_CHAL;
}

/**********************************/
/*** LOCAL FUNCTION DEFINITIONS ***/
/**********************************/
/*
 * ChapInit - Initialize a CHAP unit.
 */
static void ChapInit(int unit)
{
    chap_state *cstate = &chap[unit];

    BZERO(cstate, sizeof(*cstate));
    cstate->unit = unit;
    cstate->clientstate = CHAPCS_INITIAL;
    cstate->serverstate = CHAPSS_INITIAL;
    cstate->timeouttime = CHAP_DEFTIMEOUT;
    cstate->max_transmits = CHAP_DEFTRANSMITS;
    /* random number generator is initialized in magic_init */
}

/*
 * ChapChallengeTimeout - Timeout expired on sending challenge.
 */
static void ChapChallengeTimeout(void *arg)
{
    chap_state *cstate = (chap_state *) arg;

    /* if we aren't sending challenges, don't worry.  then again we */
    /* probably shouldn't be here either */
    if (cstate->serverstate != CHAPSS_INITIAL_CHAL &&
        cstate->serverstate != CHAPSS_RECHALLENGE)
        return;

    if (cstate->chal_transmits >= cstate->max_transmits) {
        /* give up on peer */
        CHAPDEBUG((LOG_ERR, "Peer failed to respond to CHAP challenge\n"));
        cstate->serverstate = CHAPSS_BADAUTH;
        auth_peer_fail(cstate->unit, PPP_CHAP);
        return;
    }

    ChapSendChallenge(cstate);  /* Re-send challenge */
}

/*
 * ChapResponseTimeout - Timeout expired on sending response.
 */
static void ChapResponseTimeout(void *arg)
{
    chap_state *cstate = (chap_state *) arg;

    /* if we aren't sending a response, don't worry. */
    if (cstate->clientstate != CHAPCS_RESPONSE)
        return;

    ChapSendResponse(cstate);  /* re-send response */
}

/*
 * ChapRechallenge - Time to challenge the peer again.
 */
static void ChapRechallenge(void *arg)
{
    chap_state *cstate = (chap_state *) arg;

    /* if we aren't sending a response, don't worry. */
    if (cstate->serverstate != CHAPSS_OPEN)
        return;

    ChapGenChallenge(cstate);
    ChapSendChallenge(cstate);
    cstate->serverstate = CHAPSS_RECHALLENGE;
}

/*
 * ChapLowerUp - The lower layer is up.
 *
 * Start up if we have pending requests.
 */
static void ChapLowerUp(int unit)
{
    chap_state *cstate = &chap[unit];

    if (cstate->clientstate == CHAPCS_INITIAL)
        cstate->clientstate = CHAPCS_CLOSED;
    else if (cstate->clientstate == CHAPCS_PENDING)
        cstate->clientstate = CHAPCS_LISTEN;

    if (cstate->serverstate == CHAPSS_INITIAL)
        cstate->serverstate = CHAPSS_CLOSED;
    else if (cstate->serverstate == CHAPSS_PENDING) {
        ChapGenChallenge(cstate);
        ChapSendChallenge(cstate);
        cstate->serverstate = CHAPSS_INITIAL_CHAL;
    }
}

/*
 * ChapLowerDown - The lower layer is down.
 *
 * Cancel all timeouts.
 */
static void ChapLowerDown(int unit)
{
    chap_state *cstate = &chap[unit];

    /* Timeout(s) pending?  Cancel if so. */
    if (cstate->serverstate == CHAPSS_INITIAL_CHAL ||
        cstate->serverstate == CHAPSS_RECHALLENGE)
        UNTIMEOUT(ChapChallengeTimeout, cstate);
    else if (cstate->serverstate == CHAPSS_OPEN
        && cstate->chal_interval != 0)
        UNTIMEOUT(ChapRechallenge, cstate);
    if (cstate->clientstate == CHAPCS_RESPONSE)
        UNTIMEOUT(ChapResponseTimeout, cstate);

    cstate->clientstate = CHAPCS_INITIAL;
    cstate->serverstate = CHAPSS_INITIAL;
}

/*
 * ChapProtocolReject - Peer doesn't grok CHAP.
 */
static void ChapProtocolReject(int unit)
{
    chap_state *cstate = &chap[unit];

    if (cstate->serverstate != CHAPSS_INITIAL &&
        cstate->serverstate != CHAPSS_CLOSED)
        auth_peer_fail(unit, PPP_CHAP);
    if (cstate->clientstate != CHAPCS_INITIAL &&
        cstate->clientstate != CHAPCS_CLOSED)
        auth_withpeer_fail(unit, PPP_CHAP);
    ChapLowerDown(unit);  /* shutdown chap */
}

/*
 * ChapInput - Input CHAP packet.
 */
static void ChapInput(int unit, u_char *inpacket, int packet_len)
{
    chap_state *cstate = &chap[unit];
    u_char *inp;
    u_char code, id;
    int len;

    /*
     * Parse header (code, id and length).
     * If packet too short, drop it.
     */
    inp = inpacket;
    if (packet_len < CHAP_HEADERLEN) {
        CHAPDEBUG((LOG_INFO, "ChapInput: rcvd short header.\n"));
        return;
    }
    GETCHAR(code, inp);
    GETCHAR(id, inp);
    GETSHORT(len, inp);
    if (len < CHAP_HEADERLEN) {
        CHAPDEBUG((LOG_INFO, "ChapInput: rcvd illegal length.\n"));
        return;
    }
    if (len > packet_len) {
        CHAPDEBUG((LOG_INFO, "ChapInput: rcvd short packet.\n"));
        return;
    }
    len -= CHAP_HEADERLEN;

    /*
     * Action depends on code (as in fact it usually does :-).
     */
    switch (code) {
        case CHAP_CHALLENGE:
            ChapReceiveChallenge(cstate, inp, id, len);
            break;

        case CHAP_RESPONSE:
            ChapReceiveResponse(cstate, inp, id, len);
            break;

        case CHAP_FAILURE:
            ChapReceiveFailure(cstate, inp, id, len);
            break;

        case CHAP_SUCCESS:
            ChapReceiveSuccess(cstate, inp, id, len);
            break;

        default:    /* Need code reject? */
            CHAPDEBUG((LOG_WARNING, "Unknown CHAP code (%d) received.\n", code));
            break;
    }
}

/*
 * ChapReceiveChallenge - Receive Challenge and send Response.
 */
static void ChapReceiveChallenge(chap_state *cstate, u_char *inp, int id, int len)
{
    int rchallenge_len;
    u_char *rchallenge;
    int secret_len;
    char secret[MAXSECRETLEN];
    char rhostname[256];
    MD5_CTX mdContext;
    u_char hash[MD5_SIGNATURE_SIZE];

    CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: Rcvd id %d.\n", id));
    if (cstate->clientstate == CHAPCS_CLOSED ||
        cstate->clientstate == CHAPCS_PENDING) {
        CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: in state %d\n",
               cstate->clientstate));
        return;
    }

    if (len < 2) {
        CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: rcvd short packet.\n"));
        return;
    }

    GETCHAR(rchallenge_len, inp);
    len -= sizeof (u_char) + rchallenge_len; /* now name field length */
    if (len < 0) {
        CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: rcvd short packet.\n"));
        return;
    }
    rchallenge = inp;
    INCPTR(rchallenge_len, inp);

    if (len >= sizeof(rhostname))
        len = sizeof(rhostname) - 1;
    BCOPY(inp, rhostname, len);
    rhostname[len] = '\000';

    CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: received name field '%s'\n",
           rhostname));

    /* Microsoft doesn't send their name back in the PPP packet */
    if (ppp_settings.remote_name[0] != 0 && (ppp_settings.explicit_remote || rhostname[0] == 0)) {
        strncpy(rhostname, ppp_settings.remote_name, sizeof(rhostname));
        rhostname[sizeof(rhostname) - 1] = 0;
        CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: using '%s' as remote name\n",
               rhostname));
    }

    /* get secret for authenticating ourselves with the specified host */
    if (!get_secret(cstate->unit, cstate->resp_name, rhostname,
        secret, &secret_len, 0)) {
        secret_len = 0;  /* assume null secret if can't find one */
        CHAPDEBUG((LOG_WARNING, "No CHAP secret found for authenticating us to %s\n", rhostname));
    }

    /* cancel response send timeout if necessary */
    if (cstate->clientstate == CHAPCS_RESPONSE)
        UNTIMEOUT(ChapResponseTimeout, cstate);

    cstate->resp_id = id;
    cstate->resp_transmits = 0;

    /*  generate MD based on negotiated type */
    switch (cstate->resp_type) {

        case CHAP_DIGEST_MD5:
            MD5Init(&mdContext);
            MD5Update(&mdContext, &cstate->resp_id, 1);
            MD5Update(&mdContext, (u_char*)secret, secret_len);
            MD5Update(&mdContext, rchallenge, rchallenge_len);
            MD5Final(hash, &mdContext);
            BCOPY(hash, cstate->response, MD5_SIGNATURE_SIZE);
            cstate->resp_length = MD5_SIGNATURE_SIZE;
            break;

#ifdef CHAPMS
        case CHAP_MICROSOFT:
            ChapMS(cstate, rchallenge, rchallenge_len, secret, secret_len);
            break;
#endif

        default:
            CHAPDEBUG((LOG_INFO, "unknown digest type %d\n", cstate->resp_type));
            return;
    }

    BZERO(secret, sizeof(secret));
    ChapSendResponse(cstate);
}

/*
 * ChapReceiveResponse - Receive and process response.
 */
static void ChapReceiveResponse(chap_state *cstate, u_char *inp, int id, int len)
{
    u_char *remmd, remmd_len;
    int secret_len, old_state;
    int code;
    char rhostname[256];
    MD5_CTX mdContext;
    char secret[MAXSECRETLEN];
    u_char hash[MD5_SIGNATURE_SIZE];

    CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: Rcvd id %d.\n", id));

    if (cstate->serverstate == CHAPSS_CLOSED ||
        cstate->serverstate == CHAPSS_PENDING) {
        CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: in state %d\n",
        cstate->serverstate));
        return;
    }

    if (id != cstate->chal_id)
        return;   /* doesn't match ID of last challenge */

    /*
    * If we have received a duplicate or bogus Response,
    * we have to send the same answer (Success/Failure)
    * as we did for the first Response we saw.
    */
    if (cstate->serverstate == CHAPSS_OPEN) {
        ChapSendStatus(cstate, CHAP_SUCCESS);
        return;
    }
    if (cstate->serverstate == CHAPSS_BADAUTH) {
        ChapSendStatus(cstate, CHAP_FAILURE);
        return;
    }

    if (len < 2) {
        CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: rcvd short packet.\n"));
        return;
    }
    GETCHAR(remmd_len, inp);  /* get length of MD */
    remmd = inp;   /* get pointer to MD */
    INCPTR(remmd_len, inp);

    len -= sizeof (u_char) + remmd_len;
    if (len < 0) {
        CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: rcvd short packet.\n"));
        return;
    }

    UNTIMEOUT(ChapChallengeTimeout, cstate);

    if (len >= sizeof(rhostname))
        len = sizeof(rhostname) - 1;
    BCOPY(inp, rhostname, len);
    rhostname[len] = '\000';

    CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: received name field: %s\n",
                rhostname));

    /*
    * Get secret for authenticating them with us,
    * do the hash ourselves, and compare the result.
    */
    code = CHAP_FAILURE;
    if (!get_secret(cstate->unit, rhostname, cstate->chal_name,
        secret, &secret_len, 1)) {
/*        CHAPDEBUG((LOG_WARNING, TL_CHAP, "No CHAP secret found for authenticating %s\n", rhostname)); */
        CHAPDEBUG((LOG_WARNING, "No CHAP secret found for authenticating %s\n",
        rhostname));
    }
    else {

        /*  generate MD based on negotiated type */
        switch (cstate->chal_type) {

            case CHAP_DIGEST_MD5:  /* only MD5 is defined for now */
                if (remmd_len != MD5_SIGNATURE_SIZE)
                    break;   /* it's not even the right length */
            MD5Init(&mdContext);
            MD5Update(&mdContext, &cstate->chal_id, 1);
            MD5Update(&mdContext, (u_char*)secret, secret_len);
            MD5Update(&mdContext, cstate->challenge, cstate->chal_len);
            MD5Final(hash, &mdContext);

            /* compare local and remote MDs and send the appropriate status */
            if (memcmp (hash, remmd, MD5_SIGNATURE_SIZE) == 0)
                code = CHAP_SUCCESS; /* they are the same! */
            break;

            default:
                CHAPDEBUG((LOG_INFO, "unknown digest type %d\n", cstate->chal_type));
        }
    }

    BZERO(secret, sizeof(secret));
    ChapSendStatus(cstate, code);

    if (code == CHAP_SUCCESS) {
        old_state = cstate->serverstate;
        cstate->serverstate = CHAPSS_OPEN;
        if (old_state == CHAPSS_INITIAL_CHAL) {
            auth_peer_success(cstate->unit, PPP_CHAP, rhostname, len);
        }
        if (cstate->chal_interval != 0)
            TIMEOUT(ChapRechallenge, cstate, cstate->chal_interval);
    }
    else {
        CHAPDEBUG((LOG_ERR, "CHAP peer authentication failed\n"));
        cstate->serverstate = CHAPSS_BADAUTH;
        auth_peer_fail(cstate->unit, PPP_CHAP);
    }
}

/*
 * ChapReceiveSuccess - Receive Success
 */
static void ChapReceiveSuccess(chap_state *cstate, u_char *inp, u_char id, int len)
{

    CHAPDEBUG((LOG_INFO, "ChapReceiveSuccess: Rcvd id %d.\n", id));

    if (cstate->clientstate == CHAPCS_OPEN)
    /* presumably an answer to a duplicate response */
        return;

    if (cstate->clientstate != CHAPCS_RESPONSE) {
        /* don't know what this is */
        CHAPDEBUG((LOG_INFO, "ChapReceiveSuccess: in state %d\n",
               cstate->clientstate));
        return;
    }

    UNTIMEOUT(ChapResponseTimeout, cstate);

    /*
     * Print message.
     */
    if (len > 0)
        PRINTMSG(inp, len);

    cstate->clientstate = CHAPCS_OPEN;

    auth_withpeer_success(cstate->unit, PPP_CHAP);
}

/*
 * ChapReceiveFailure - Receive failure.
 */
static void ChapReceiveFailure(chap_state *cstate, u_char *inp, u_char id, int len)
{
    CHAPDEBUG((LOG_INFO, "ChapReceiveFailure: Rcvd id %d.\n", id));

    if (cstate->clientstate != CHAPCS_RESPONSE) {
        /* don't know what this is */
        CHAPDEBUG((LOG_INFO, "ChapReceiveFailure: in state %d\n",
               cstate->clientstate));
        return;
    }

    UNTIMEOUT(ChapResponseTimeout, cstate);

    /*
     * Print message.
     */
    if (len > 0)
        PRINTMSG(inp, len);

    CHAPDEBUG((LOG_ERR, "CHAP authentication failed\n"));
    auth_withpeer_fail(cstate->unit, PPP_CHAP);
}

/*
 * ChapSendChallenge - Send an Authenticate challenge.
 */
static void ChapSendChallenge(chap_state *cstate)
{
    u_char *outp;
    int chal_len, name_len;
    int outlen;

    chal_len = cstate->chal_len;
    name_len = strlen(cstate->chal_name);
    outlen = CHAP_HEADERLEN + sizeof (u_char) + chal_len + name_len;
    outp = outpacket_buf[cstate->unit];

    MAKEHEADER(outp, PPP_CHAP);  /* paste in a CHAP header */

    PUTCHAR(CHAP_CHALLENGE, outp);
    PUTCHAR(cstate->chal_id, outp);
    PUTSHORT(outlen, outp);

    PUTCHAR(chal_len, outp);  /* put length of challenge */
    BCOPY(cstate->challenge, outp, chal_len);
    INCPTR(chal_len, outp);

    BCOPY(cstate->chal_name, outp, name_len); /* append hostname */

    pppWrite(cstate->unit, outpacket_buf[cstate->unit], outlen + PPP_HDRLEN);

    CHAPDEBUG((LOG_INFO, "ChapSendChallenge: Sent id %d.\n", cstate->chal_id));

    TIMEOUT(ChapChallengeTimeout, cstate, cstate->timeouttime);
    ++cstate->chal_transmits;
}

/*
 * ChapSendStatus - Send a status response (ack or nak).
 */
static void ChapSendStatus(chap_state *cstate, int code)
{
    u_char *outp;
    int outlen, msglen;
    char msg[256];

    if (code == CHAP_SUCCESS)
        strcpy(msg, "Welcome!");
    else
        strcpy(msg, "I don't like you.  Go 'way.");
    msglen = strlen(msg);

    outlen = CHAP_HEADERLEN + msglen;
    outp = outpacket_buf[cstate->unit];

    MAKEHEADER(outp, PPP_CHAP);  /* paste in a header */

    PUTCHAR(code, outp);
    PUTCHAR(cstate->chal_id, outp);
    PUTSHORT(outlen, outp);
    BCOPY(msg, outp, msglen);
    pppWrite(cstate->unit, outpacket_buf[cstate->unit], outlen + PPP_HDRLEN);

    CHAPDEBUG((LOG_INFO, "ChapSendStatus: Sent code %d, id %d.\n", code,
           cstate->chal_id));
}

/*
 * ChapGenChallenge is used to generate a pseudo-random challenge string of
 * a pseudo-random length between min_len and max_len.  The challenge
 * string and its length are stored in *cstate, and various other fields of
 * *cstate are initialized.
 */

static void ChapGenChallenge(chap_state *cstate)
{
    int chal_len;
    u_char *ptr = cstate->challenge;
    int i;

    /* pick a random challenge length between MIN_CHALLENGE_LENGTH and 
       MAX_CHALLENGE_LENGTH */
    chal_len = (unsigned)
                ((((magic() >> 16) *
                    (MAX_CHALLENGE_LENGTH - MIN_CHALLENGE_LENGTH)) >> 16)
                 + MIN_CHALLENGE_LENGTH);
    cstate->chal_len = chal_len;
    cstate->chal_id = ++cstate->id;
    cstate->chal_transmits = 0;

    /* generate a random string */
    for (i = 0; i < chal_len; i++)
        *ptr++ = (char) (magic() & 0xff);
}

/*
 * ChapSendResponse - send a response packet with values as specified
 * in *cstate.
 */
/* ARGSUSED */
static void ChapSendResponse(chap_state *cstate)
{
    u_char *outp;
    int outlen, md_len, name_len;

    md_len = cstate->resp_length;
    name_len = strlen(cstate->resp_name);
    outlen = CHAP_HEADERLEN + sizeof (u_char) + md_len + name_len;
    outp = outpacket_buf[cstate->unit];

    MAKEHEADER(outp, PPP_CHAP);

    PUTCHAR(CHAP_RESPONSE, outp); /* we are a response */
    PUTCHAR(cstate->resp_id, outp); /* copy id from challenge packet */
    PUTSHORT(outlen, outp);   /* packet length */

    PUTCHAR(md_len, outp);   /* length of MD */
    BCOPY(cstate->response, outp, md_len);  /* copy MD to buffer */
    INCPTR(md_len, outp);

    BCOPY(cstate->resp_name, outp, name_len); /* append our name */

    /* send the packet */
    pppWrite(cstate->unit, outpacket_buf[cstate->unit], outlen + PPP_HDRLEN);

    cstate->clientstate = CHAPCS_RESPONSE;
    TIMEOUT(ChapResponseTimeout, cstate, cstate->timeouttime);
    ++cstate->resp_transmits;
}

/*
 * ChapPrintPkt - print the contents of a CHAP packet.
 */
static int ChapPrintPkt(
    u_char *p,
    int plen,
    void (*printer) (void *, char *,...),
    void *arg
    )
{
    int code, id, len;
    int clen, nlen;
    u_char x;

    if (plen < CHAP_HEADERLEN)
        return 0;
    GETCHAR(code, p);
    GETCHAR(id, p);
    GETSHORT(len, p);
    if (len < CHAP_HEADERLEN || len > plen)
        return 0;

    if (code >= 1 && code <= sizeof(ChapCodenames) / sizeof(char *))
        printer(arg, " %s", ChapCodenames[code-1]);
    else
        printer(arg, " code=0x%x", code);
    printer(arg, " id=0x%x", id);
    len -= CHAP_HEADERLEN;
    switch (code) {
        case CHAP_CHALLENGE:
        case CHAP_RESPONSE:
            if (len < 1)
                break;
        clen = p[0];
        if (len < clen + 1)
            break;
        ++p;
        nlen = len - clen - 1;
        printer(arg, " <");
        for (; clen > 0;--clen) {
            GETCHAR(x, p);
            printer(arg, "%.2x", x);
        }
        printer(arg, ">, name = %.*Z", nlen, p);
        break;
        case CHAP_FAILURE:
        case CHAP_SUCCESS:
            printer(arg, " %.*Z", len, p);
            break;
        default:
            for (clen = len; clen > 0;--clen) {
                GETCHAR(x, p);
                printer(arg, " %.2x", x);
            }
    }

    return len + CHAP_HEADERLEN;
}

#endif

#endif /* PPP_SUPPORT */
